1. Field of the Invention
The present invention relates to control circuits able to auto-configure two extrinsic LED arrays either in parallel or in series in accordance with the detection result of the AC input voltage range. The LED illuminating apparatuses auto-configured with the aid of disclosed control circuits could support dual-range (both 100±20% V and 200±20% V) operation, enabling a wider range of acceptable AC input.
2. Description of the Prior Art
As compared with the traditional lighting devices, the LED has a higher luminous efficacy. The LEDs can give off more than 100 lumens per watt because less electric energy is converted into waste heat. In sharp contrast, a traditional bulb only gives off about 15 lumens per watt because more electric energy is converted into waste heat. Moreover, LED-based lighting devices are gradually becoming preferred the lighting equipment because of having a relatively longer lifetime to reduce maintenance cost, being less susceptible to exterior interference, and being less likely to get damaged.
Technically, LEDs need to be DC-driven. So, an AC sinusoidal voltage source would normally be rectified by a full-wave or half-wave rectifier into a rectified sinusoidal voltage source before coming into use. Besides, the traditional AC-to-DC LED drivers usually require buck or boost converters to step down or up a rectified sinusoidal voltage source to a proper DC voltage level for normal operation, ending up with tons of shortcomings such as bulky and heavy design, conducted and radiated EMI, short lifetime, high cost, and so forth.
Traditional AC-direct LED light engines are only for single-range (either 100±20% V or 200±20% V) operation, narrowing the acceptable range of the AC input. To widen the acceptable range of the AC input, the inventors came up with the control circuits for series or parallel auto-configuration. With the aid of the disclosed control circuits for series or parallel auto-configuration, traditional AC-direct LED light engines could be easily upgraded from single-range (either 100±20% V or 200±20% V) operation to dual-range (both 100±20% V and 200±20% V) operation so as to enable a wider acceptable range of the AC input for worldwide applications.
In a nutshell, the main purpose of the present invention is to create control circuits so as to upgrade single-range (either 100±20% V or 200±20% V) operation to dual-range (both 100±20% V and 200±20% V) operation.